Konstantina Lambrinou

Profile Information
Name
Konstantina Lambrinou
Institution
Institute for Nuclear Materials Science
Position
Scientific collaborator
Publications:
"(Nbx, Zr1-x)4AlC3 MAX Phase Solid Solutions: Processing, Mechanical Properties, and Density Functional Theory Calculations" Konstantina Lambrinou, Inorganic Chemistry Vol. 55 2016 5445-5452 Link
The solubility of zirconium (Zr) in the Nb4AlC3 host lattice was investigated by combining the experimental synthesis of (Nbx, Zr1-x)4AlC3 solid solutions with density functional theory calculations. High-purity solid solutions were prepared by reactive hot pressing of NbH0.89, ZrH2, Al and C starting powder mixtures. The crystal structure of the produced solid solutions was determined using X-ray and neutron diffraction. The limited Zr solubility (maximum 18.5% of the Nb-content in the host lattice) in Nb4AlC3 observed experimentally is consistent with the calculated minimum in the energy of mixing. The lattice parameters and microstructure were evaluated over the entire solubility range, while the chemical composition of (Nb0.85, Zr0.15)4AlC3 was mapped using atom probe tomography. The hardness, Young’s modulus and fracture toughness at room temperature, as well as the high-temperature flexural strength and E-modulus of (Nb0.85, Zr0.15)4AlC3 were investigated and compared to those of pure Nb4AlC3. Quite remarkably, an appreciable increase in fracture toughness was observed from 6.6 +/- 0.1 MPa.m1/2 for pure Nb4AlC3 to 10.1 +/- 0.3 MPa.m1/2 for the (Nb0.85, Zr0.15)4AlC3 solid solution.
"Corrosion scales on various steels after exposure to liquid lead–bismuth eutectic" Konstantina Lambrinou, Journal of Nuclear Materials Vol. 450 2013 244-255 Link
Several steels were exposed to either static or flowing liquid lead-bismuth eutectic under various exposure conditions. Steels T91, EP-823, S2439 and S2440 were exposed to oxygen-rich static LBE at 490C for about 5016 h. The experiments in flowing LBE were carried out in the CORRIDA loop at 550C and around 10-6 mass% dissolved oxygen. The steels tested in the CORRIDA loop included the reduced activation steel EUROFER 97 and two heats of an oxide dispersion strengthened steel produced by mixing EUROFER 97 and yttria powders. The exposure time varied between 1007 and 7511 h for the EUROFER 97 steel and between 5012 and 20039 h for the two ODS heats. The exposed steels were characterized by means of scanning electron microscopy and energy-dispersive X-ray spectrometry.
"Dissolution corrosion of 316L austenitic stainless steels in contact with static liquid lead-bismuth eutectic (LBE) at 500C" Remi Delville, Konstantina Lambrinou, Journal of Nuclear Materials Vol. 490 2017 9-27 Link
This work addresses the dissolution corrosion behaviour of 316L austenitic stainless steels. For this purpose, solution-annealed and cold-deformed 316L steels were simultaneously exposed to oxygen-poor (< 10-8 mass%) static liquid lead-bismuth eutectic (LBE) for 253-3282 h at 500C. Corrosion was consistently more severe for the cold-drawn steels than the solution-annealed steel, indicating the importance of the steel thermomechanical state. The thickness of the dissolution-affected zone was non-uniform, and sites of locally-enhanced dissolution were occasionally observed. The progress of LBE dissolution attack was promoted by the interplay of certain steel microstructural features (grain boundaries, deformation twin laths, precipitates) with the dissolution corrosion process. The identified dissolution mechanisms were selective leaching leading to steel ferritization, and non-selective leaching; the latter was mainly observed in the solution-annealed steel. The maximum corrosion rate decreased with exposure time and was found to be inversely proportional to the depth of dissolution attack.
"Synthesis of MAX Phases in the Hf-Al-C System" Konstantina Lambrinou, Inorganic Chemistry Vol. 55 2016 10922-10927 Link
For the first time, MAX phases in the Hf-Al-C system were experimentally synthesised using reactive hot pressing. HfC was observed as the main competing phase. The lattice parameters of Hf2AlC and Hf3AlC2 were determined by Rietveld refinement based on the X-ray diffraction data. The atomic stacking sequence was revealed by high-resolution scanning transmission electron microscopy. Mixtures of 211 and 312 stacking were observed within the same grain, including 523 layers. This transition in atomic structure is discussed.
"Synthesis of MAX Phases in the Zr-Ti-Al-C System" Remi Delville, Konstantina Lambrinou, Inorganic Chemistry Vol. 56 2017 3489-3498 Link
This study reports on the synthesis and characterization of MAX phases in the (Zr,Ti)n+1AlCn system. The MAX phases were synthesized by reactive hot pressing and pressureless sintering in the 1350-1700°C temperature range. The produced ceramics contained large fractions of 211 and 312 (n=1 and 2) MAX phases, while strong evidence of a 413 (n=3) stacking was found. Moreover, (Zr,Ti)C, ZrAl2, ZrAl3, and Zr2Al3 were present as secondary phases. In general, the lattice parameters of the hexagonal 211 and 312 phases followed Vegard's law over the complete Zr-Ti solid solution range, but the 312 phase showed a non-negligible deviation from Vegard's law around the (Zr0.33,Ti0.67)3Al1.2C1.6 stoichiometry. High-resolution scanning transmission electron microscopy combined with X-ray diffraction demonstrated ordering of the Zr and Ti atoms in the 312 phase, whereby Zr atoms occupied preferentially the central position in the close-packed M6X octahedral layers. The same ordering was also observed in 413 stackings present within the 312 phase. The decomposition of the secondary (Zr,Ti)C phase was attributed to the miscibility gap in the ZrC-TiC system.
"Synthesis of the new MAX phase Zr2AlC" Konstantina Lambrinou, Journal of the European Ceramic Society Vol. 36 2016 1847-1853 Link
This study reports on the first experimental evidence of the existence of the Zr2AlC MAX phase, synthesised by means of reactive hot pressing of a ZrH2, Al and C powder mixture. The crystal structure of this compound was investigated by X-ray and neutron diffraction. The lattice parameters were determinedand confirmed by high-resolution transmission electron microscopy. The effect of varying the synthesis temperature was investigated, indicating a relatively narrow temperature window for the synthesis of Zr2AlC. ZrC was always present as a secondary phase by hot pressing in the 1475–1575?C range.
"Synthesis of the novel Zr3AlC2 MAX phase" Michel Barsoum, Konstantina Lambrinou, Journal of the European Ceramic Society Vol. 36 2015 943-947 Link
Herein we report, for the first time, on the synthesis and structural characterization of the Zr-based MAX phase, Zr3AlC2, fabricated by reactive hot pressing of ZrH2, Al, and C powders. The crystal structure of Zr3AlC2 was determined by X-ray diffraction and high resolution scanning transmission electron microscopy to be the hexagonal space group P63/mmc. The a and c lattice parameters of Zr3AlC2 are 3.33308(6) Å and 19.9507(3) Å, respectively. The samples include the secondary phases ZrC and Zr-Al intermetallics as confirmed by quantitative electron probe microanalysis. The Vickers hardness (3 kg) of Zr3AlC2 was measured to be 4.4 ±0.4 GPa.
"Twin boundary-accelerated ferritization of austenitic stainless steels in liquid lead–bismuth eutectic" David Frazer, Peter Hosemann, Konstantina Lambrinou, Erich Stergar, Scripta Materialia Vol. 118 2016 37-40 Link
Exposure of austenitic stainless steels to liquid lead-bismuth eutectic with low concentration of dissolved oxygen typically results in selective leaching of highly-soluble alloying elements and ferritization of the dissolution-affected zone. In this work, focused ion beam, transmission electron backscatter diffraction and scanning transmission electron microscopy were utilised to elucidate early-stage aspects of the dissolution corrosion process of cold-worked austenitic stainless steels exposed to static, oxygen-poor liquid lead-bismuth eutectic at 450C for 1000 hours. It was found that deformation-induced twin boundaries in the cold-worked steel bulk provide paths of accelerated penetration of the liquid metal into the steel bulk.
Presentations:
"MAX phase materials for nuclear applications" Konstantina Lambrinou, ICACC 2016 January 24-29, (2016) Link
NSUF Articles:
U.S. DOE Nuclear Science User Facilities Awards 35 Rapid Turnaround Experiment Research Proposals - Awards total approximately $1.3 million These projects will continue to advance the understanding of irradiation effects in nuclear fuels and materials in support of the mission of the DOE Office of Nuclear Energy. Wednesday, September 20, 2017 - Calls and Awards
DOE Awards 37 RTE Proposals - Awarded projects total nearly $1.4M in access awards Tuesday, July 14, 2020 - News Release, Calls and Awards